JP5194450B2 - Turbo molecular pump - Google Patents

Description

  The present invention relates to a turbo molecular pump.

  2. Description of the Related Art Conventionally, a turbo molecular pump compatible with a high gas load having a turbo molecular pump portion including a moving blade and a stationary blade and a screw pump portion including a screw rotor and a screw stator screw is known (see, for example, Patent Document 1) ). In such a turbo molecular pump, in order to avoid the accumulation of reaction products in the pump, an exhaust port is provided in a housing provided with a screw stator, and heating means for heating the housing and the exhaust port to a predetermined temperature is provided. I have.

JP 2005-249068 A

  By the way, in order to improve the performance of the screw pump section, it is necessary to enlarge the diameter of the screw stator or to extend it in the direction of the exhaust port. When extending in the direction of the exhaust port, there is a problem that the pump body becomes larger in the axial direction in order to avoid a reduction in the opening area of the exhaust port due to the downward extension of the screw stator.

According to the first aspect of the present invention, a turbo pump portion, a screw pump portion, a substantially cylindrical housing provided with a screw stator of the screw pump portion, a side surface of the housing, and a downstream space of the screw pump portion and the outside of the pump communicate with each other. And an exhaust port having an opening that is covered with the lower end of the screw pump portion and having an upper portion covered by the lower end portion of the screw pump portion, and an exhaust port on both sides of the exhaust port of the cylindrical hole. A gas passage that communicates with the exhaust port at a position that bites in the longitudinal direction and guides the gas in the downstream space from both sides of the exhaust port to the exhaust port, and the gas passage is formed over the entire inner peripheral surface of the housing. , A ring-shaped groove that cuts out a part of the side circumference of the exhaust port, and the sum of the conductance of the openings on both sides where the gas passage communicates with the exhaust port of the cylindrical hole is the screw pump part at the opening part of the exhaust port Under Characterized in that it is comparable to the conductance of the covered part fractionated by parts.
According to a second aspect of the present invention, in the turbomolecular pump according to the first aspect, the screw stator is formed integrally with the housing.
According to a third aspect of the present invention, in the turbomolecular pump according to the first aspect, the screw stator is provided separately from the housing and is fixed to the housing by a bolt.

  According to the present invention, since the gas passage for guiding the gas in the downstream space from the side periphery of the exhaust port to the exhaust port is provided, the opening area of the exhaust port can be increased while suppressing an increase in the size of the pump. .

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a turbo molecular pump according to the present invention. The turbo molecular pump shown in FIG. 1 is a turbo molecular pump compatible with a high gas load, and is composed of a turbo pump portion composed of rotor blades 20 and stator blades 30, a screw rotor portion 21, and a screw stator portion 31. And a screw pump unit.

  The rotor blade 20 and the screw rotor portion 21 are formed in the rotor 2, and the stator blade 30 and the screw stator portion 31 are provided in the housing 3. The rotor 2 is supported in a non-contact manner by radial magnetic bearings 41 and 42 and a thrust magnetic bearing 43 provided on the spindle 4 and is driven to rotate by a motor 44.

  Spacers 32 are disposed between the plurality of stator blades 30 stacked on the housing 3, and the stator blades 30 and the spacers 32 are connected to the upper end of the casing and the housing 3 by bolting the casing 5 to the housing 3. Sandwiched between. Each stator blade 30 is positioned at a predetermined position by a spacer 32.

  Gas molecules that have flowed from the intake port of the casing 5 are blown down in the figure by the turbo pump unit, and are compressed and exhausted toward the downstream side. The compressed gas molecules are further compressed by the screw pump unit, and reach a downstream space (hereinafter referred to as a back pressure space) S formed in the lower portion of the housing 5. The gas in the back pressure space S is exhausted to the outside by an auxiliary pump connected to the exhaust port 33. Although not shown, an exhaust flange 35 for connecting an auxiliary pump is attached to the exhaust port 33 (see FIG. 2).

  FIG. 2 is a diagram showing in detail the screw pump portion and the exhaust port portion. FIG. 2A is a cross-sectional view of the present embodiment shown in FIG. FIG. 2B shows a conventional case in which the axial length of the screw pump portion is shorter than that shown in FIG. Since the screw stator portion 31 is formed of a screw groove formed in the housing 3, as shown in FIG. 2A, the inner peripheral surface of the screw stator portion 31 is more than the inner peripheral surface of the back pressure space S in which the exhaust port 33 is provided. The gas flow from the thread groove to the back pressure space S is not hindered.

  In the case of FIG. 2B, the axial distance L between the lower end of the screw stator portion 31 formed in the housing 3 and the surface of the spindle, that is, the axial dimension of the back pressure space (downstream space) S of the screw pump portion. By setting L to be larger than the inner diameter D of the exhaust port 33, the same opening area as the cross-sectional area of the exhaust port 33 is secured for the back pressure space S. The housing 3 is temperature-controlled by a heater 50 and a cooling water pipe 51 in order to prevent reaction products from accumulating.

  In FIG. 2B, when the screw rotor portion 21 and the screw stator portion 31 are expanded downward as indicated by a two-dot chain line in order to improve the performance of the screw pump portion, the portion indicated by the symbol B of the opening portion of the exhaust port 33 is the screw stator portion. It will be blocked by 31. As a result, the opening area on the back pressure space S side of the exhaust port 33 is reduced, and an adverse effect on the exhaust performance due to a decrease in conductance occurs. For example, if the conductance of the circular opening before enlargement is C1, and the conductance of the semicircular opening after enlargement is C2, C2 is about half of C1 in the state shown in FIG.

  In the turbo molecular pump shown in FIG. 2A, a ring-shaped groove 34 that is recessed from the inner peripheral surface of the housing toward the outer peripheral surface is formed in the lower portion of the screw stator portion 31. The groove 34 is formed so as to bite in from the opening on the back pressure space S side of the exhaust port 33 toward the outlet opening direction (right direction in the drawing). FIG. 3A is a view of the housing 3 as seen from the bottom side, and FIG. As shown in FIG. 3, the groove 34 is formed in a ring shape over the entire circumference of the inner peripheral surface.

  FIG. 4 is an enlarged cross-sectional view of the exhaust port 33 portion. In the opening on the back pressure space side of the exhaust port 33, a portion indicated by a symbol B is closed by a screw stator portion 31, and this portion is the same as the conventional one shown in FIG. However, since the groove 34 is formed so as to bite into the exhaust port 33, a part of the peripheral surface of the exhaust port 33 is notched, and two openings 33 a communicating with the back pressure space S through the groove 34 are formed. Will be. As a result, a sufficient opening area can be ensured.

  For example, if the conductance of the opening 33a is C3, it is considered that the overall conductance is approximately C2 + C3 + C3 due to the formation of the opening 33a. Therefore, if the groove 34 is set so that C2 + C3 + C3 = C1, conductance comparable to that in the case of FIG. 2B can be ensured.

  Therefore, even when the axial dimension L of the back pressure space (downstream space) S is smaller than the inner diameter D of the exhaust port 33, the opening area of the exhaust port 33 increases due to the formation of the groove 34, and the back pressure space. A decrease in conductance from S to the gas flowing into the exhaust port 33 through the groove 34 can be prevented. In this case, the groove 34 functions as a gas passage to the exhaust port 33. As a result, the exhaust performance of the screw pump unit can be improved while suppressing an increase in the axial dimension of the turbo molecular pump. Further, even if the groove 34 is formed, the shape of the housing bottom surface 36 does not change, so that there is no problem in fixing the spindle 4.

  Here, the groove 34 is formed in a ring shape, but may not necessarily be a ring shape, and may be a groove having a predetermined length extending in the left-right direction including the exhaust port 33. The gas in the back pressure space S flows into the groove 34 and then flows into the exhaust port 33 from the opening 33a on the side surface of the exhaust port.

  By the way, in the above-described example, the case where the screw stator portion 31 is expanded downward has been described. However, even in the condition of L> D as in the conventional pump as shown in FIG. If the groove 34 is formed so as to bite into the groove, a notch opening is formed in the peripheral surface as in the case of FIG. 2A, so that the conductance can be improved.

  In the above-described embodiment, the magnetic bearing type turbo molecular pump has been described as an example. However, the present invention is not limited to the magnetic bearing type and can be applied. Further, although the screw groove 31 is formed on the inner peripheral surface of the housing 3 and the screw stator 31 is formed integrally with the housing 3, the screw stator portion 31 may be provided separately from the housing 3 as shown in FIG. The screw stator 31 is fixed to the housing 3 by bolts 37. The present invention can be applied not only to the magnetic bearing type turbo molecular pump.

  In the correspondence between the embodiment described above and the elements of the claims, the back pressure space S constitutes the downstream space, the groove 34 constitutes the gas passage, and the inner diameter D of the exhaust port 33 constitutes the axial opening size. . The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims.

It is a figure which shows one Embodiment of the turbo-molecular pump by this invention. It is a figure which shows the part of a screw pump part and an exhaust port in detail, (a) shows the case of this Embodiment, (b) shows the conventional case. It is a figure which shows the housing 3, (a) is the figure seen from the bottom face side, (b) is a C arrow line view. It is sectional drawing which expanded and showed the part of the exhaust port 33. FIG. It is a figure which shows the screw stator part 31 provided separately from the housing.

Explanation of symbols

  2: Rotor, 3: Housing, 4: Spindle, 20: Rotor blade, 21: Screw stator section, 30: Stator blade, 31: Screw rotor section, 33: Exhaust port, 34: Groove, 36: Housing bottom surface, S: Back pressure space

Claims (3)

A turbo pump section;
Screw pump,
A substantially cylindrical housing provided with a screw stator of the screw pump part;
An exhaust port that is formed on a side surface of the housing and includes a cylindrical hole having a predetermined length that communicates with the downstream space of the screw pump unit and the outside of the pump, and has an opening that is covered with the lower end of the screw pump unit. When,
The both sides of the exhaust port of the cylindrical hole communicate with the exhaust port at a position biting in the longitudinal direction of the exhaust port with respect to the opening of the exhaust port, and the gas in the downstream space is passed to both sides of the exhaust port. A gas passage that leads from the exhaust to the exhaust port,
The gas passage is a ring-shaped groove that is formed over the inner peripheral surface of the housing and cuts out a part of the side periphery of the exhaust port.
The total conductance of each side periphery of the opening communicating the gas passage outlet of the tubular hole, at the opening of the exhaust port, in parts of the conductance comparable covered by the lower end portion of the screw pump section A turbo molecular pump characterized by being. The turbo-molecular pump according to claim 1 ,
The turbomolecular pump, wherein the screw stator is formed integrally with the housing. The turbo-molecular pump according to claim 1,
The turbo-molecular pump, wherein the screw stator is provided separately from the housing and is fixed to the housing by a bolt.

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